Yes, it's worth it, or no one in their right mind would be doing it.
Most of those things are very much common sense.
Pharmacy--why wouldn't you check to make sure that they did indeed send up Ampicillin 1g IVPB and not Gentamycin or Clindamycin or PO amoxicillin? And check that it's the right patient? I'd want to do that even if it weren't my legal obligation to do so. NOW-if pharmacy sent you up with a bag Labled "Magnesium Sulfate 20 grams in 500mL Steril H2O" and you run it at the rate prescribed--let's say 50 cc/hr which is 2 grams per hour, and the patient developes magnesium toxicity because the bag actually contained 500grams in 500mLs (very unlikely, but let's just use it for number's sake)-THAT is not your fault. Although, hopefully you were assessing the Pt as per protocol, picked up on the s/s of Mag Tox and intervened in time.
LPNsCNAs--If the CNA is supposed to do a finger stick at 10pm, then you need to make sure that not only was it done, but that it was within normal limits for that patient. Again, forget about legalities here. Wouldn't you want to know that your patient's blood sugar is 450 BEFORE the resident notices it at 6am rounds? I sure would. (FTR-for the most part, the CNAs I've worked with were great as far as notifying the RN or LPN about results, etc)
Doctors--If a doctor ordered Tylenol 975mg q4h PRN, yes, you should know that that's too much. If he orders Amoxicillin 500mg PO when the Pt. is severely allergic to PCN, yes, you should know that there's an error there. In the begining especially (but also the seasoned nurse)-look things up in the PDR. If a dosage seems weird, ask the doctor. Sometimes there's a real reason-ie with Cytotec. Usually it's a once daily PO med (when used for preventing ulcers). In inducing labor or abortion, it can be inserted vaginally or rectally, sometimes a few pills at a time. Either way, you stand to learn a lot.